This application relates to a power electronics cooling system wherein a plurality of motor controllers are provided with a single cooling system, and wherein the flow leading to the motor controllers is adjusted dependent on conditions at cold start-up of the aircraft.
Power electronics are becoming widely utilized in many applications. One particular application is the use of motor controllers on an aircraft. As aircraft become more and more complex, more sophisticated high power motors provide various functions. In one system, motor controllers are provided with a single cooling system which circulates a cooling fluid such that the motor controllers are maintained at an acceptable temperature during use.
The motor controllers may provide any number of functions. Some of the functions are required to be operational upon initial start-up of the aircraft, while others can be left off for a period of time until the cooling system can warm up.
Some of the larger motor controllers have a flow orifice that provides a high volume of cooling fluid, while other of the motor controllers may have a flow orifice that provides a limited amount of cooling fluid. The amount of cooling fluid is typically determined by the amount of cooling required at operational conditions. Thus, a large motor controller would typically require greater cooling fluid volume. On the other hand, some of the smaller motor controllers must be operational upon initial start-up of the aircraft, and thus demand cooling fluid initially.
A problem can occur, particularly at initial start-up in very cold conditions, for example, below −30 C. At initial start-up in very cold conditions, the viscosity of the cooling fluid can be very high, and thus there may be a tendency for the cooling fluid to flow in undesirable volumes to the larger motor controllers having a larger orifice, resulting in an insufficient amount of cooling fluid being delivered to the smaller motor controllers.
In the prior systems, it has been known to increase the system pressure for the cooling fluid. This may somewhat overcome the orifice pressure drop mentioned above during cold conditions. However, this also requires cooling system components such as cold plates, cooling lines, pumps and valves, which are all necessarily designed for the higher system pressure. These components thus become larger, heavier, and more expensive, which is all undesirable.